Uncollapsing the wavefunction by undoing quantum measurements

We review and expand on recent advances in theory and experiments concerning the problem of wavefunction uncollapse: Given an unknown state that has been disturbed by a generalized measurement, restore the state to its initial configuration. We describe how this is probabilistically possible with a subsequent measurement that involves erasing the information extracted about the state in the first measurement. The general theory of abstract measurements is discussed, focusing on quantum information aspects of the problem, in addition to investigating a variety of specific physical situations and explicit measurement strategies. Several systems are considered in detail: the quantum double dot charge qubit measured by a quantum point contact (with and without Hamiltonian dynamics), the superconducting phase qubit monitored by a SQUID detector, and an arbitrary number of entangled charge qubits. Furthermore, uncollapse strategies for the quantum dot electron spin qubit, and the optical polarization qubit are also reviewed. For each of these systems the physics of the continuous measurement process, the strategy required to ideally uncollapse the wavefunction, as well as the statistical features associated with the measurement is discussed. We also summarize the recent experimental realization of two of these systems, the phase qubit and the polarization qubit.Comment: 19 pages, 4 figure

Long-wavelength TCF-based fluorescence probes for the detection and intracellular imaging of biological thiols

Two ‘turn on’ TCF-based fluorescence probes were developed for the detection of biological thiols (TCF-GSH and TCFCl-GSH). TCF-GSH was shown to have a high sensitivity towards glutathione (GSH) with a 0.28 μM limit of detection. Unfortunately, at higher GSH concentrations the fluorescence intensity of TCF-GSH decreased and toxicity was observed for TCF-GSH in live cells. However, TCFCl-GSH was shown to be able to detect GSH at biologically relevant concentrations with a 0.45 μM limit of detection. No toxicity was found for TCFCl-GSH and a clear ‘turn on’ with good photostability was observed for the exogenous addition of GSH, Cys and HCys. Furthermore, TCFCl-GSH was used to evaluate the effects of drug treatment on the levels of GSH in live cells

Boronate ester cross-linked PVA hydrogels for the capture and H2O2-mediated release of active fluorophores

A new set of PVA hydrogels were formed using the boronate ester fluorescent probe, PF1 and the novel boronate fluorescent probe PT1 as the covalent crosslinkers. Treatment with aqueous H2O2 allowed triggered release of the fluorescent dye accompanied by complete dissolution of the hydroge

Applied utility and the auto-ethnographic short story: persuasions for, and illustrations of, writing critical social science

In some quarters it is argued that, narrative researchers might be classified as being either storyanalysts or storytellers. They go on to suggest that one feature of storytellers is that they undertake a form of analysis as the process of writing unfolds. With these sentiments in mind, in the present paper, we consider how auto-ethnographical accounts of traumatic and challenging life events might, through the analysis contained within, demonstrate value within the realm of applied pedagogy. In making our case we embrace and adapt the literary genre of storytelling, more specifically, the short story. The story presented here, ‘Travel Writer’, offers an opaque, multicontextualised and lifelong view of career transition. The present paper, in more general terms, considers the capacity of auto-ethnography and, more specifically, the short storied version of it, to engender critical reader engagement, to encourage personal reflection in others, and to act as a point of stimulus for the enactment of applied debate through the lens of critical social science. With regards to the assumptions of critical social science, the final discussion also considers how the auto-ethnographic text, as a pedagogic tool, might help others to contest and challenge the meta-narratives that, we argue, risk stagnating established thinking

Stochastic Behavior of Effective Field Theories Across Threshold

We explore how the existence of a field with a heavy mass influences the low energy dynamics of a quantum field with a light mass by expounding the stochastic characters of their interactions which take on the form of fluctuations in the number of (heavy field) particles created at the threshold, and dissipation in the dynamics of the light fields, arising from the backreaction of produced heavy particles. We claim that the stochastic nature of effective field theories is intrinsic, in that dissipation and fluctuations are present both above and below the threshold. Stochasticity builds up exponentially quickly as the heavy threshold is approached from below, becoming dominant once the threshold is crossed. But it also exists below the threshold and is in principle detectable, albeit strongly suppressed at low energies. The results derived here can be used to give a quantitative definition of the `effectiveness' of a theory in terms of the relative weight of the deterministic versus the stochastic behavior at different energy scales.Comment: 32 pages, Latex, no figure

Spontaneous emission in a planar Fabry-Perot microcavity

Published versio

TCF-ALP: a fluorescent probe for the selective detection of Staphylococcus bacteria and application in "smart" wound dressings

Alkaline phosphatase (ALP) is an important enzyme-based biomarker present in several bacterial species; however, it is currently undervalued as a strategy to detect pathogenic bacteria. Here, we explore our ALP-responsive colorimetric and fluorescent probe (TCF-ALP) for such applications. TCF-ALP displayed a colorimetric and fluorescence response towards Staphylococcus aureus (S. aureus), with a limit of detection of 3.7 × 106 CFU mL−1 after 24 h incubation. To our surprise, TCF-ALP proved selective towards Staphylococcus bacteria when compared with Enterococcus faecalis (E. faecalis), and Gram-negative P. aeruginosa and E. coli. Selectivity was also seen in clinically relevant S. aureus biofilms. Owing to the high prevalence and surface location of S. aureus in chronic wounds, TCF-ALP was subsequently encapsulated in polyvinyl alcohol (PVA)-based hydrogels as a proof-of-concept “smart” wound dressing. TCF-ALP hydrogels were capable of detecting S. aureus in planktonic and biofilm assays, and displayed a clear colour change from yellow to purple after 24 h incubation using ex vivo porcine skin models. Overall, TCF-ALP is a simple tool that requires no prior knowledge, training, or specialist equipment, and has the potential to overcome issues related to invasive swabbing and tissue biopsy methods. Thus, TCF-ALP could be used as a tool to monitor the early development of infection in a wound and allow for the rapid provision of appropriate treatment for Staphylococcal bacterial infections

Sequence Comparisons of Odorant Receptors among Tortricid Moths Reveal Different Rates of Molecular Evolution among Family Members

In insects, odorant receptors detect volatile cues involved in behaviours such as mate recognition, food location and oviposition. We have investigated the evolution of three odorant receptors from five species within the moth genera Ctenopseustis and Planotrotrix, family Tortricidae, which fall into distinct clades within the odorant receptor multigene family. One receptor is the orthologue of the co-receptor Or83b, now known as Orco (OR2), and encodes the obligate ion channel subunit of the receptor complex. In comparison, the other two receptors, OR1 and OR3, are ligand-binding receptor subunits, activated by volatile compounds produced by plants - methyl salicylate and citral, respectively. Rates of sequence evolution at non-synonymous sites were significantly higher in OR1 compared with OR2 and OR3. Within the dataset OR1 contains 109 variable amino acid positions that are distributed evenly across the entire protein including transmembrane helices, loop regions and termini, while OR2 and OR3 contain 18 and 16 variable sites, respectively. OR2 shows a high level of amino acid conservation as expected due to its essential role in odour detection; however we found unexpected differences in the rate of evolution between two ligand-binding odorant receptors, OR1 and OR3. OR3 shows high sequence conservation suggestive of a conserved role in odour reception, whereas the higher rate of evolution observed in OR1, particularly at non-synonymous sites, may be suggestive of relaxed constraint, perhaps associated with the loss of an ancestral role in sex pheromone reception